A "4D" systemic view on meridian essence: Substantial, functional, chronological and cultural attributes

The term Jingluo, translated as meridian or channel, is a core component of traditional Chinese medicine (TCM) and has played a fundamental role in guiding the clinical practice of acupuncture for thousands of years. However, the essence of the meridian remains elusive and is a source of both confusion and debate for researchers. In this study, a "4D" systemic view on the essence of the meridian, namely substantial, functional, chronological, and cultural dimensions, was proposed based on a review of the ancient medical classics, recent research developments, and results from clinical practice. Previous studies have primarily focused on the substantial dimension of the meridian system, with scant interpretation about its functional domain. Neither systemic data nor evaluations have been adequately documented. Additionally, a limited but increasing number of studies have focused on the chronological and cultural dimensions. More investigations that embody the holistic concept of TCM and integrate the systemic modes and advanced techniques with dominant diseases of TCM need to be performed to obtain a more comprehensive understanding of the essence of meridians. The goal of this study is to yield useful information in understanding the essence of meridians and provide a reference and perspective for further research.